Dual connectivity is a foundational feature of current 5G NR Non-Standalone (NSA) networks, allowing various ways for LTE and 5G base stations and devices to connect, while using the LTE core.
As operators start to move towards 5G Standalone, and the 5G core, they will have new dual connectivity challenges. Since it will be many years before most operators turn off 4G, there will be continuing work on the most efficient ways for the two networks to interoperate. And there will be other issues related to 5G’s wide choice of spectrum bands, including the introduction of millimeter wave frequencies into mainstream multiband macro networks.
Qualcomm and its arch-rival in smartphone chips, MediaTek, were both active in dual connectivity trials for 5G SA in recent weeks.
Qualcomm announced that it had aggregated sub-6 GHz FDD spectrum with 28 GHz mmWave airwaves to support dual connectivity in an SA environment; and then it did the same with sub-6 GHz TDD spectrum and 39 GHz mmWave. Enabling dual connectivity of sub-6 GHz and mmWave bands could help operators improve the levels of access to 5G SA networks by using midband spectrum for broad coverage, without having to fall back to LTE very often, while offloading high capacity processing to mmwWave.
That could improve quality of experience and eventually make it easier for operators to start to switch off 4G, or at least repurpose some of its spectrum for 5G. The world’s largest 5G SA deployment to date, by T-Mobile USA, has suffered from some reports that coverage is reduced compared to NSA.
Qualcomm used emulators from Keysight Technologies during data calls conducted on March 17. , 2021.
Meanwhile, Ericsson and MediaTek were working on similar tests, demonstrating dual connectivity of 60 MHz of midband spectrum with 800 MHz in millimeter wave on commercial hardware and chipsets. This achieved speeds of up to 5.1Gbps on an individual device, in SA mode. The test used a MediaTek M80 5G modem with Ericsson RAN and 5G core.
The NR DC technology for 5G SA, which was used in both tests, works alongside carrier aggregation to boost performance.
“NR DC allows user equipment to be connected to two serving nodes and in each node it is possible to connect multiple carriers using the carrier aggregation technique,” Patrik Persson, strategic product manager for 5G RAN at Ericsson, told FierceWireless. “The two technologies coexist to maximize the available spectrum towards the device. NR DC is defined to be only used in Standalone 5G since the master node must be connected to 5G core network.”
Ericsson expects commercial release of 5G NR DC functionality in the third quarter.